Recently, Internet telephony has been gaining world-wide popularity. Internet telephony involves the use of a multimedia personal computer (PC) or handheld device to complete Voice Over Internet Protocol (VOIP) calls using the Internet as a transport medium. Gateways have even been established in various cities in order to permit VOIP calls to be completed to a regular telephone on the Switched Telephone Network (STN).
While VOIP appears to be an attractive alternative to the traditional Public Service Telephone Network (PSTN) voice connections, it has remained foreign to small-office/home-office and consumers for various reasons. First, difficulty in configuration and installation has discouraged retailers because of technical support issues. In addition, a limited availability of public Internet addresses available to Digital Subscriber (DSL) customers limits the number of users on a network. Typically, ninety percent (90%) of the currently installed DSL connections have only one public address available. This address is usually taken with a single PC, or multiple PCs sharing the one public address by use of a DSL Network Address Translating (NAT) router.
The above problems once plagued the PC industry, where multiple PCs could not share one connection to the Internet because only one address was available. Thus, NAT DSL routers solved the problem of limited addresses by masquerading many private Internet addresses into one public Internet address, while at the same time solving the technical support issues by removing the difficulty of configuring the PC by utilizing Dynamic Host Configuration Protocol (DHCP). These NAT routers have become very popular, as millions are installed thru-out the world.
Because VOIP protocols send address information embedded within the data portion of the protocol packet, the masquerading process of NAT routers is insufficient for such protocols. The ability to deliver a public call to a private VOIP device located behind the NAT router also poses problems preventing VOIP devices from utilizing NAT routers to solve the problems above.
Therefore, a mechanism to enable VOIP communications, with multiple plug and play VOIP devices, with both incoming (called) and outgoing (calling) capability, all operating behind one NAT router sharing one public Internet address, is desired.